In a Manhattan building by architect John Pawson, interior decorator Mica Ertegun fashions a sophisticated setting for an art dealer’s blue-chip collection

There was a time when the ultimate definition of a Manhattan apartment with “good bones” was a classically inflected space authored by Stanford White, Rosario Candela, Emery Roth, or a similar arbiter of prewar architectural taste. But with the recent efflorescence of showstopping residential buildings by many of the world’s most acclaimed modern architects, good bones in Gotham are no longer the sole province of the old masters. Consider the pristine, supremely understated Gramercy Park edifice designed in 2006 by John Pawson, the British monarch of minimalism. Few structures in the city can boast bones as good as these.

“I was astonished that my client chose a place that wasn’t in the middle of the city,” says Mica Ertegun of MAC II, who decorated an expansive apartment for a gallerist and scion of a family of elite New York art dealers. “But he’s a young man, so he didn’t want a conventional arrangement. The building is fresh and modern, and it has genuine quality.”

The owner had begun his search for living quarters in 2009, scouring Chelsea, SoHo, and the Lower East Side for a home with a contemporary sensib ility distinct from the traditional environs of the Upper East Side, a neighborhood where Ertegun and her late partner in MAC II, Chessy Rayner, have left an indelible imprint.

In 2010, after seeing nearly 50 apartments around the city, the dealer alighted on a 2,400-square-foot space in the 17-story Pawson building, with bronze-framed floor-to-ceiling windows overlooking Gramercy Park—a historic urban Eden open exclusively to area residents—and a generous 640-square-foot terrace ideal for entertaining his friends.

“This is my first time making an apartment,” he says. “I wanted to be somewhere that had real energy—this place has the feeling of a loft without the challenges of living in a loft space. There are lots of good walls for hanging art, and the terrace really sealed the deal.”

Working within the footprint established by Pawson, Ertegun and her client made only slight changes to the existing quarters, preserving signature details such as the broad limestone fireplace surround in the living room and a cherry bookcase in the dining room. Minor emendations included annexing a walk-in dressing room off the master suite to create a small home office and lightening the bedroom’s dark mahogany walls and cabinetry with a special finish that approximates the look of cerused oak, effectively tempering the gravitas of the space.

The goal of the limited renovation was “to make a comfortable home where our client could relax, watch sports, and welcome his friends,” Ertegun explains. “We kept all the fabrics and paint colors neutral so they wouldn’t compete with the paintings and drawings. The main thing here is the art.”

Surprisingly, the works on display are not restricted to artists represented by the client’s venerable gallery. Instead, blue-chip pieces by such 20th-century icons as Lucian Freud, Martin Kippenberger, Willem de Kooning, and Andy Warhol mingle amicably with contemporary sculptures, paintings, and photographs by Adel Abdessemed, Mark Grotjahn, Andreas Gursky, and others. The revolving mix includes objects that straddle the line between art and design, among them a set of three painted cube tables by Richard Woods, which the homeowner acquired in 2010 during the annual Art Basel Miami Beach fair.

“I’m constantly bringing in new works and rehanging the collection,” he says. “There’s no better way to test a particular piece than to live with it. You find out if you really connect with the artist.”

The array of American and European furnishings Ertegun assembled for the apartment favors handsome, unpretentious midcentury pieces by the likes of Milo Baughman, John Kandell, and Charlotte Perriand. Idiosyncratic items such as a vintage glass-top display table with a sculptural base of steel railroad spikes add a personal touch.

“The furniture is distinctly modern, but there’s nothing crazy or precious. It’s all meant to be very livable—you can put a drink down anywhere and not have to worry,” Ertegun says.

To make the most of the commodious terrace and to lend it a little privacy from the units above, steel pergolas fitted with automated retractable canvas awnings and beams of sustainably harvested ipe, a Brazilian hardwood, were installed, along with slatted ipe walls and banquettes. Dining and cocktail tables of limestone and Giacometti-style powder-coated steel stools, all custom designed by MAC II, complete the inviting terrace-scape. It’s every space-starved New Yorker’s dream.

“I’ve known the family forever and worked with all of them over the years, so the process of making this home was not difficult,” Ertegun says. “Our client has inherited good taste and marvelous paintings, and he has an apartment built to show them to their best advantage.